In the fields of medicines, cosmetics, food, agricultural chemicals, and the like, many useful substances have the property of being hardly soluble in water. Such property limits utilization of the useful substances. In general, a method such as mechanical micronization, addition of a solubilizing agent, or the like is employed in order to solubilize the hardly water-soluble substances. As the solubilizing agent, in many cases, an organic solvent, an emulsifier, a surfactant, cyclodextrin, or the like that is soluble in water is used. However, there are some hardly water-soluble substances that cannot be solubilized with the use of such solubilizing agent.
A carbon nanotube is theoretically expected to have excellent chemical, electronic, and mechanical properties, and these properties have been confirmed by experiments in recent years. There have been studies for using the carbon nanotube for, for example, electron emitting devices, fuel cells, composite materials, semiconductors, a probe for scanning probe microscopes, electromagnetic wave shielding materials, medical materials, and the like by utilizing the excellent properties thereof, and part of the studies have been put into practical use. The carbon nanotube is classified into a single-layer carbon nanotube formed of one graphite layer only and a multilayer carbon nanotube formed of a plurality of graphite layers that are overlapped in the form of coaxial cylinders. Among the carbon nanotubes, the single-layer carbon nanotube is especially insoluble to many solvents, and since the surface thereof has a strong hydrophobicity, it is not soluble to water at all. Such insolubility features largely limit chemical utilization of the carbon nanotubes and the single-layer carbon nanotube in particular, especially when the chemical utilization requires dissolution or dispersion of carbon nanotubes into solvents. As a result, the insolubility features are one of the factors that limit the applicable fields of the carbon nanotubes.
Methods for dispersing the carbon nanotube into a solvent have heretofore been disclosed. One of them is a method of chemically modifying the surface of a carbon nanotube (see Non-Patent Document 1). However, the chemically modified carbon nanotube obtained by this method is different from the carbon nanotube before the chemical modification in chemical, electronic, and mechanical properties due to the chemical modification. Therefore, the inherent excellent properties of the carbon nanotube can not be utilized.
As a method for dispersing a carbon nanotube while maintaining original properties of the carbon nanotube, there is a method of wrapping with a polymer in a non-covalent bonding manner (i.e. polymer wrapping method). Dispersion into an organic solvent employing this method is disclosed in Non-Patent Documents 2 and 3 and the like, and dispersion into water employing this method is disclosed in Patent Document 1 and Non-Patent Document 4.
Further, as to the dispersion into water, there has been disclosed a method of dispersing a carbon nanotube by adsorbing an amphiphatic compound such as a surfactant to a side wall of the carbon nanotube. As for such amphiphatic compound, an amphiphatic ammonium salt compound (Non-Patent Document 5) a surfactant (Non-Patent Document 6), a synthetic peptide (Non-Patent Document 7), cationic lipid and DNA (Patent Document 2), starch (amylose and amylopectin) (Non-Patent Documents 8, 9 and 10), DNA (Non-Patent Document 11), cyclodextrin (Non-Patent Documents 12), β-1,3-glucan (Non-Patent Document 13), and a water-soluble polysaccharide (Patent Documents 3 and 4), for example, have been disclosed.
When eating rice, wheat and buckwheat as well as processed grain foods such as rice, bread, noodle, and the like that are processed foods thereof, starch contained therein is generally gelatinized by generally cooking. The processed grain foods have most preferable physical properties such as color, glossiness, non-stickiness, and the like immediately after cooking, and after that, the physical properties are deteriorated overtime, such as change in color, loss of glossiness on surface, or sticking by increase in adhesion property are caused due to drying, aging of starch, and the like.
It is noted that, as used herein, the term “adhesion” refers to a phenomenon that food materials stick to each other in the processed grain food and it is made uneasy to unstick them. Specifically, it refers to the stickiness of a grain, noodles or skins of grains. More specifically, it refers to the phenomenon that grains of rice becoming hardly separate due to the binding of rice grains, spaghetti becoming hardly separate due to the binding of noodles, a plurality of dumplings becoming hardly separate due to the binding of skins of the plurality of dumplings, and the like. When food materials of the processed grain food are stuck with each other, it becomes difficult to eat the food, and further, the texture of the food is deteriorated, resulting in considerable reduction in food value.
When eating the processed grain food, it is desirable to eat them as soon as possible after cooking, but in the case of the processed grain food that are sold in restaurants, distribution stores, and the like, a longer period of time passes until eating due to the time required for production and distribution. During such time, the processed grain food loses the preferable physical properties of immediately after cooking, and the value of the food is considerably reduced.
Various proposals have been made in order to solve such problems for the processed grain food.
Patent Document 5 describes an non-stickiness improver for a processed grain food including a water-soluble hemicellulose, as well as a processed grain food obtained by adding the non-stickiness improver to a grain food or a processed grain food (e.g. rice or pasta) or by treating its surface with the non-stickiness improver. Patent Document 6 describes a formulation for noodle production containing at least one organic acid or organic acid salt and a water-soluble hemicellulose. Patent Document 7 describes a production method for instant dried noodles characterized in that a noodle is treated before drying with a water-soluble hemicellulose. Patent Document 8 describes a quality improver for a processed grain food characterized by containing a water-soluble hemicellulose and monoglyceride acetate. Patent Document 9 describes a non-stickiness improver obtained by emulsifying a mixture containing oil, a viscous polysaccharide, and a water-soluble hemicellulose. The water-soluble hemicellulose described in Patent Documents 5 to 9 is those obtained from an herbaceous plant such as an oilseed (soybean, palm, corn and cotton seed) and grains (wheat and rice). A main ingredient of the water-soluble hemicellulose of oilseed is a polygalactan in which main chain of it is a polymer of galactose. For example, in Examples of Patent Document 8, a water-soluble hemicellulose whose trade name is Soyafive is used. A main ingredient of Soyafive-S is a polygalactan mainly composed of galactose, galacturonic acid, arabinose, and rhamnose. The structure of the polygalactan is totally different from those of the water-soluble xylan of the present invention.    Patent Document 1: Japanese National Phase PCT Laid-Open Publication No. 2004-506530 (page 2)    Patent Document 2: Japanese Laid-open Patent Document No. 2004-82663 (page 1)    Patent Document 3: Japanese Laid-open Patent Document No. 2005-14332 (page 1)    Patent Document 4: Japanese National Phase PCT Laid-Open Publication No. 2004-531442 (page 2)    Patent Document 5: Japanese Laid-open Patent Document No. 6-121647 (page 2)    Patent Document 6: Japanese Laid-open Patent Document No. 2000-139385 (page 2)    Patent Document 7: Japanese Laid-open Patent Document No. 2000-139387 (page 2)    Patent Document 8: Japanese Laid-open Patent Document No. 2000-222550 (page 2)    Patent Document 9: Japanese Laid-open Patent Document No. 2005-13135 (page 2)    Non-Patent Document 1: “Science”, vol. 282, P95 (1998)    Non-Patent Document 2: “J. Phys. Chem. B.”, vol. 104, P10012 (2000)    Non-Patent Document 3: “J. Am. Chem. Soc.”, vol. 124, P9034 (2002)    Non-Patent Document 4: “Chemical Physics Letters”, vol. 342, P265 (2001)    Non-Patent Document 5: “Chemistry Letters”, P638 (2002)    Non-Patent Document 6: “Applied Physics A”, vol. 69, P269 (1998)    Non-Patent Document 7: “J. Am. Chem. Soc.”, vol. 125, P1770 (2003)    Non-Patent Document 8: “Angew. Chem Int. Ed.”, vol. 41, P2508 (2002)    Non-Patent Document 9: “Carbohydrate Polymers”, vol. 51, P93 (2003)    Non-Patent Document 10: “Carbohydrate Polymers”, vol. 51, P311 (2003)    Non-Patent Document 11: “Chemistry Letters”, vol. 32, P456 (2003)    Non-Patent Document 12: “Chem. Commun.”, P986 (2003)    Non-Patent Document 13: “J. Am. Chem. Soc.”, vol. 127, P5875 (2005)